Paranymph
A paranymph is a ceremonial assistant and/or coach in a ceremony. In ancient Greek weddings the bride and bridegroom were attended by paranymphs, and from this use it has been generalized to refer to attendants of doctoral students, best men and bridesmaids in weddings and the like. It can refer specifically to the friend of a bridegroom tasked with accompanying him in a chariot to fetch the bride home.